Instrument standardization

Z. Y. Wang, T. Dean and B.R. Kowalski, Additive background correction in multivariate instrument standardization. Anal. Chem., 67 (1995) 2379-2385. 

M. L. Magee, J. T. On mass spectrometer instrument standardization and interlaboratory calibration transfer using neural networks. Anal. Chim. Acta 1997,384, 511-532. 

It is also important to note that matrix-related effects, either signal enhancement or more commonly signal suppression, can have a pronounced effect on quantitative measurements. Based on these observations, the use of isotope-labeled standards is helpful to achieve accurate analytical measurement data on the diastereoisomers. Several methods found in the open literature include use of both 13C-labeled and d18-labeled surrogates as recovery and/or instrument standards [118],... 

Instrument standardization, v - a procedure for standardizing the response of multiple instruments such that a common multivariate model is applicable for measurements conducted across these instruments, the standardization being accomplished via adjustment of the spectrophotometer hardware or via mathematical treatment of one or a series of collected spectra. 

In any setup, it is paramount that the electrodes get cleaned regularly. The minimum frequency, e.g., once a week, should be described in the instrument standard operation procedure (SOP), but for some methods or samples more frequent cleaning is necessary. An example is the determination of the enantiomeric purity of adrenaline in local anesthetic solutions. The samples are isotonic and contain high concentrations of local anesthetics (5—20mg/ml). The determination concerns very low concentrations of adrenaline (typically 5 pg/ml of 1-form and only a few percent of that of the d-form) and the samples are therefore injected undiluted. Furthermore, relatively high concentrations of cyclodextrin are present in the BGE. Eong sequences therefore require electrode cleaning for every sequence and this is thus described in the method procedure. ... 

Standardization The instrument response function can vary from analyzer to analyzer. If calibration transfer is to be achieved across all instrument platforms it is important that the instrument function is characterized, and preferably standardized [31]. Also, at times it is necessary to perform a local calibration while the analyzer is still on-line. In order to handle this, it is beneficial to consider an on-board calibration/standardization, integrated into the sample conditioning system. Most commercial NIR analyzers require some form of standardization and calibration transfer. Similarly, modem FTIR systems include some form of instrument standardization, usually based on an internal calibrant. This attribute is becoming an important feature for regulatory controlled analyses, where a proper audit trail has to be established, including instrument calibration. 

Concurrent with the selection of transfer standards is the selection of the optimal strategy deciding whether to use calibration transfer or instrument standardization, assigning the master and slave instruments, and selecting a suitable transfer algorithm. Some commonly used algorithms for calibration transfer and instrument standardization are discussed below. 

Multiway methods For analyzer data where a single sample generates a second order array (ex. GC/MS, LC/UV, excitation/emission fluorescence), multiway chemometric modehng methods, such as PARAFAC (parallel factor analysis) [121,122], can be used to exploit the second order advantage to perform effective calibration transfer and instrument standardization. 

Good Laboratory Practice (GLP) The system provides a comprehensive feature set to aid customers in meeting GLP requirements. This includes features such as certificate-of-software validation, user-access levels, instrument and sequence logbooks, system-suitability software for aU supported HP instruments, standard GLP reports, and a GLP save option that encrypts and saves data and methods together. 

Pumping systems are apparently well established, and nothing really new appeared in the different reviews on instrumentation. Standard 316 stainless steel wetted components provide superior corrosion resistance to most system fluids. 

Only three of the metals, rhodium, palladium and platinum, need be considered. Of these only rhodium plating is of significant commercial importance, but the relatively low cost of palladium has made it attractive for contacts and printed circuits. Electrodeposited platinum is harder than the annealed bulk metal and finds applications in jewellery, the plating of scientific instruments, standard weights and parts of electrical apparatus. 

Another important issue that arises in the PDS method, as well as some other standardization methods, is the selection of the samples to use for standardization. It is critical that the standardization samples efficiently convey the magnitude and nature of instrument-to-instrument variability artifacts that are expected to be present in the analyzers while they are operating in the field. Note that this criterion is different than the criterion used for sample selection for calibration, which is to sufficiently cover the compositions of the process samples that the analyzer is expected to see during its operation. Sample selection strategies for instrument standardization have been given by many.73,77-79... 

Wang, Y., Lysaght, M.J. and Kowalski, B.R., Improvement of Multivariate Calibration through Instrument Standardization Anal. Chem. 1992, 64, 562-564. 

Instrument Turbidity mean values measured (FNU) and instrumental standard deviation (FNU) at a nominal value of turbidity of ... 

Acceptance Used as a routine, standard method Development of fully automated methods for high throughput analysis open access instruments standard methods outsourcing. 

Table 1 summarises the most important results from the investigation of metal doping. In this table the results of MAP treatment are combined with effects of firing temperature and doping. As can be seen in Table 1, y-alumina membranes with pore radii as low as 2.0 nm (Kelvin radius) may be obtained after firing at 600°C. Note that an instrumental standard error of 0.5 nm (90% reliability) is common in permporometry. This technique should therefore only be used for comparison purposes and to obtain a qualitative impression of the pore-size and pore-size distribution of the material under investigation. 

Either PLS or PCR can be used to compute b, at less than full rank by discarding factors associated with noise. Because of the banded diagonal structure of the transformation matrix used by PDS, localized multivariate differences in spectral response between the primary and secondary instrument can be accommodated, including intensity differences, wavelength shifts, and changes in spectral bandwidth. The flexibility and power of the PDS method has made it one of the most popular instrument standardization methods. 

Calibration transfer, n - a method of applying a multivariate calibration developed on one instrument to data measured on a different instrument, by mathematically modifying the calibration model or by a process of instrument standardization. 

Materials (chemicals, instrumentation, standards, etc.) required in the transfer standards should be supplied with certificates of analysis... 

Another important attribute of the candidate instrument is that its response to mercury should be independent of the form in which it is found in the sample. The NIC instrument thermally decomposes the sample and converts all of the mercury to the elemental form, thereby ensuring that instrument response is independent of the mercury species. This enables the analyst to use a stable ionic form of mercury in an acidified aqueous medimn for the purpose of instrument standardization. 

---